It's hard to juxtapose this picture with the sexually explicit death-row groupie Kidman portrays in the indie drama The Paperboy and it's even more confusing when she earnestly insists she is shy.

''My New Year's resolution actually [was] to get out more, to go out and be part of the world, because my nature is very introverted,'' she says. ''And I have a tendency to stay home and be very insulated and just be with my family. So I'm pushing myself and instead of going, 'I'm just going to get in my pyjamas and go to bed,' I'm going out to dinners and parties a bit more.''

Those who know the 45-year-old actress well say her shyness was often misinterpreted as coldness during her decade as Mrs Tom Cruise. But these days, the star of films including Dead Calm, To Die For, Moulin Rouge, The Hours and Australia comes across much warmer and more comfortable in her own skin. It could be attributed to just getting older or the happiness she has found with singer Keith Urban, her husband of six years, and their two daughters, Sunday, 4, and Faith, 2.

In The Paperboy she plays Charlotte Bless, a trashy southern American sexpot who recruits a Miami Times reporter (Matthew McConaughey) and his smitten brother (Zac Efron) to help her prove the innocence of her latest death-row boyfriend (John Cusack). It is not just a performance that earned her nominations in last month's Golden Globe and Screen Actors Guild awards in the US. It is a transformation.

Efron, on whose character Bless urinates to treat a jellyfish sting in a controversial scene, agrees. ''I was just as shocked as my character,'' the actor says of Kidman's masturbatory performance opposite Cusack in a no-touching prison sex scene his character witnesses. ''John and Nicole were on this wavelength and not breaking character and she just went for it and afterwards it was like she woke up and said, 'Where am I?' It was pretty crazy.''

Not one to talk at length about her process, Kidman reveals that she and Cusack had an understanding. ''The only way I met John was as the character and at the end of the film, he came to my trailer and said, 'Hi, I'm John,''' she says. ''Because if I'd been relating to him as myself, I wouldn't have been able to do that scene at all.''

The Paperboy is directed by Lee Daniels, whose edgy 2009 drama Precious won an Oscar for supporting actress Mo'Nique. Kidman went after the role as soon as she read the script.

''I just never get asked to do roles like that, particularly not as I've got further along in my career. And that's a frustration as an actor when you're looking to stretch yourself,'' she says.

''I think the raw sexuality of this role was something that terrified me. But, at the same time, I wanted to work with Lee Daniels on this because I thought it would be something I've never been able to do before. I used to jump out of planes when I was younger, and I must somehow still be addicted to that feeling, that you jump and hope when you pull the cord there will be a parachute there.''

Kidman vows her children will never see the film - and she's not sure about her Sydney-based parents, either. But her husband had no problem with her new screen persona.

''I loved it. She's hot in that movie, I've got to say,'' Urban said recently. ''I love that she's an artist who has the courage and willingness to go and explore a character that's very uncomfortable or might be misunderstood.''

Kidman lights up when talking about family. She shows me photos of her daughters on her phone and seems eager to finish press duties and head back to her adopted home of Nashville, where she has a vegetable garden and makes frequent trips to Starbucks and yoga classes without a second glance from paparazzi.

''It's a really down-to-earth, protected life there,'' she says. ''Movies are non-existent there because it's the centre of country music, so I'm kind of on the periphery, and that's a really nice place to be for me.''

When Urban finishes his stint on American Idol later this year, Kidman is looking forward to their next adventure.

''He's going on tour and we tell Sunday and Faith it's a family road trip,'' she says, giggling. ''We all go out on the tour bus and it's actually very relaxing for me because I'm not worrying about performing when he's the one doing shows every night.''

From widow to a state of grace

The Paperboy is the first of four films Australian audiences will see from Nicole Kidman in the next 12 months.

The others include:

   Stoker Kidman plays an unstable widow who is infatuated with her late husband's brother (Matthew Goode) but suspicious of his agenda with her daughter (Mia Wasikowska). ''It's interesting … to start off with a discordant mother-daughter relationship and play a woman who just wants to be loved,'' Kidman says.

   The Railway Man Based on a true story about a Scottish prisoner of war (Colin Firth) on the Burma railway who returns years later, with the help of his wife (Kidman), to meet one of his torturers to let go of his hate. ''I found it really inspiring, and that's what drew me to it - the power of somebody loving someone through trauma,'' she says.

  Grace of Monaco The story of Hollywood star Grace Kelly's involvement with a tax dispute between her new husband, Prince Rainier III of Monaco, and French president Charles de Gaulle. ''It's a film, not a documentary,'' Kidman says. ''So my job was to come up with what I felt was her heartbeat, but only for that period we're depicting, when she was still making the transition from movie star to princess.''

The Paperboy is released  on February 28.